Stabilized fuel antiknock



STABILIZED FUEL ANTIKNOCK Eugene F. Hill, Detroit, Mich, assignor toEthyl Corporation, New York, N. Y., a corporation of DelawareApplication October 20, 1951, Serial No. 252,399

9 Claims. (Cl. 44-69) No Drawing.

This invention relates to the stabilization of antiknock compounds andto the stabilization of motor fuels containing such antiknocks.

The fuel requirements of the modern internal combustion spark ignitionengine are such that each ingredient of such fuels must maintain thequality and original characteristics present when the fuels wereblended. In order to provide the high octane rating required by highcompression internal combustion engines, it is customary to include in'the fuel an antiknock additive. Of such additives the most widely usedis tetraethyllead. The amount of tetraethyllead employed in hydrocarbonfuels varies with the type of fuel and with the type of engine in whichit is to be used. For example for use in automotive engines it iscustomary to employ between about 0.5 and 3 cc. of tetraethyllead pergallon of fuel, depending upon the lead susceptibility and quality ofthe base stock. On the other hand for use in aircraft engines the amountof tetraethyllead employed is ordinarily between the limits of about 3and 6 cc. per gallon of fuel. Under unusual circumstances each of theselimits can be varied although the above figures are commonplace underpresent fuel and engine conditions. Along with tetraethyllead ascavenging agent is employed which upon combustion of the fuel combineswith the products of combustion of the tetraethyllead to place the leadin a condition wherein it can be discharged from the engine withoutcausing unnecessary build up of solid deposits on the internal surfacesof the combustion chamber, the spark plugs or the inlet or exhaustvalves. The most common practice is to employ an organic halogencompound as a scavenger. The most common of the scavenging agentscomprise ethylene dichloride and ethylene dibromide. However, recently awide variety of halogen compounds having particularly desirableproperties have been developed. Among such scavenging agents aredibromotoluene, trichlorobenzene, bromoxylene and the like.

Although by ordinary chemical standards the tetraethyllead and thehalogen scavenging agents can be considered as stable materials, undercertain conditions, a small amount of decomposition occurs. In spite ofthe slowness and limited extent of such decomposition, thisdecomposition can become important and in many instances critical to thesatisfactory operation of an internal com bustion engine. Although themechanism of such decomposition is not clearly understood, the finalproducts of such degradation have been established as being caused bythe interaction of the halogen scavenging agents and some primarydecomposition product of the tetraethyllead. The evidence of suchdecomposition is ordinarily a haze or even a sludge precipitate, eitherin the concentrated antiknock fiuid or in the finished gasoline.Regardless of the mechanism involved in this decomposition the fuelbecomes deteriorate thereby. The net result, aside from mechanicaldifficulties caused by the precipitated solids, such as plugged filtersand fuel lines and deposition in carburetor jets and on inlet mani-Ankh,

I atent folds, the fuel loses octane rating and is unable to perform asspecified in the engine.

It is therefore an object of my invention toprovide means for preventingthe decomposition of tetraethyllead antiknock compounds. It is a furtherobject to provide a concentrated antiknock material which is stable onstorage, manufacture or handling and to further provide fuels forinternal combustion engines containing tetraethyllead antiknockcompounds which are likewise stable on storage, manufacture, handling oruse. Still further objects will be apparent from the description of myinvention hereinafter.

The above and other objetcs of my invention can be accomplished byproviding tetraethyllead antiknock mixtures containing a minorproportion of Z-aminodiphenylamine. These objects can be achieved eitherby combining the Z-aminodiphenylamine with the tetraethyllead in thepresence or absence of halogen scavengers or by includingsaid2-aminodiphenylamine in motor fuel containing tetraethyllead.

It is known in general that certain aromatic amines are capable ofpreventing the degradation of hydrocarbon fuels in the presence ofoxygen. Such degradation ordinarily is evidenced by gum formation in thefuel or gum deposition on engines in which such degraded fuels have beenemployed. In general this problem with regard to the fuel is distinctfrom the problem described heretofore of stabilizing the tetraethylleadantiknock compound. In this latter problem the role of oxygen is littleunderstood, and its significance has not been established. Typicalconditions under which excessive decomposition of antiknock compoundscan occur include drum storage of the concentrated antiknock fluid underconditions of constant high temperature, as encountered in desertstorage, or under conditions of cycling high and low temperatures asfrequently encountered in transportation of such fluids throughout theworld. Likewise gasolines or other motor fuels containing such antiknockcompounds are frequently subjected to similar conditions with resultantdeterioration of the antiknock component.

This problem has been recognized for some time and a number ofsuggestions have been made for preventing such decomposition. Howevernone of these suggestions has been completely satisfactory. Todemonstrate the exceptional degree of stability imparted to antiknockcompounds and the extremely minor quantities of my stabilizer which itis required to employ I have performed the following determinations.

Example I To a fuel consisting essentially of isooctane, which isnormally resistant to deterioration, was added 4.6 ml. of tetraethylleadper gallon. The tetraethyllead was previously admixed with one theory ofethylene dibromidethat is it contained the amount of ethylene dibromidewhich is required to react under combustion conditions with thetetraethyllead to convert all the tetraethyllead to lead bromide. Onehundred milliliters of this fuel was placed in a stainless steel bombwhich was sealed and heated to a temperature of C. for a period of 16hours. At the end of this time the bomb was cooled to a temperature ofabout 25 (3., opened and the contents removed to a glass bottle. It wasobserved that the fuel which was initially clear and transparentcontained a heavy precipitate or sludge containing lead and bromine.

The above operations were repeated but before subjecting the fuel to thehigh temperature varying amounts of 2-aminodiphenylamine were added toeach of several samples of the above fuel. After a series ofdeterminations, the minimum quantity of the additive was establishedwhich would permit the fuel to be heated under these conditions for thisperiod of time without the formation of a haze or any visibleprecipitate. From these results it was established that theZ-aminodiphenylamine, the stabilizer of my invention, was elfectiveunder these conditions at the extremely small concentration of 0.05 mg.per 100 ml. of fuel.

As an alternative to the addition of the stabilizing compounds of myinvention to the hydrocarbon fuel containing the lead antiknock compoundI can achieve equally good protection by introducing the stabilizer tothe concentrated antiknock fluid. This, of course, is the preferredmethod of practicing my invention under conditions wherein the fluid issubjected to adverse storage or handling conditions. For example I canadd Z-aminodiphenylamine in amounts between 0.01 and 3.00 weight percent of the tetraethyllead present in an antiknock fluid containingethylene dibromide as the principal scavenger, a mixture of the ethylenedibromide and ethylene dichloride, or other scavengers such as forexample dibromotoluene, trichloro' benzene and bromoxylene. Thefollowing examples will serve to illustrate this embodiment of myinvention.

Example II To an antiknock compound comprising 100 parts oftetraethyllead with /2 theory of ethylene dibromide and 1 theory ofethylene dichloride, wherein the term theory has the same meaning asabove, was added 0.1 part by weight of 2-aminodiphenylamine. Theresulitng fluid was maintained at a temperature of 104 F. for a periodof one month. At the end of this time the fluid was clear-that is itcontained no precipitated solids or haze. A determination of the extentof decomposition of the tetraethyllead was made by extracting the fluidwith an aqueous ammonia solution and determining the amount of lead soextracted. Thus was determined the so-called ammonia-soluble lead, adirect measure of the extent of decomposition of the tetraethyllead. Thefresh fluid contained 0.25 gram of ammonia-soluble lead per 100 ml. oftetraethyllead in the fluid. After storage as above in the presence of0.1 weight per cent Z-aminodiphenylamine the ammonia-soluble lead wasonly 0.45 gram per 100 ml. of tetraethyllead, or an increase of only 80per cent. In contrast, this same antiknock compound was stored as abovewithout the prior addition of 2-aminodiphenylamine and developed, afterone month, 2.18 grams of ammoniasoluble lead, per 100 ml. of thetetraethyllead, an increase of 770 per cent.

Example II! An antiknock compound designed for use in aircraft enginesconsisting of tetraethyllead and one theory of ethylene dibromide, and asmall quantity of an oil soluble blue dye and to which had been added0.1 part by weight of Z-aminodiphenylarnine per 100 parts by weight oftetraethyllead in the fluid was stored at a temperature of 104 F. forone month. At the end of this period the fluid was observed and found tocontain no precipitate or haze and when viewed with a strong light, thefluid possessed the original clear blue color. Determination of theammonia-soluble lead as in Example II showed only 0.24 gram of lead per100 ml. of tetraethyllead present, compared to 0.15 gram per 100 ml. inthe original fluid.

In a duplicate determination wherein 4-aminodiphenylamine was employedin place of the Z-aminodiphenylamine at a concentration of 1 part byweight per 100 parts of tetraethyllead in the fluid of Example III, theammoniasoluble lead after one months storage at a temperature of 104 F.was 1.74 grams per 100 ml. of tetraethyllead. Thus, even at times theconcentration a seven-fold increase in the amount of amomnia-solublelead occurred in contrast to Z-aminodiphenylamine. Thus, my stabilizerwas over 70 times as effective on a weight basis. In a controldetermination, the above fluid, in the absence of a stabilizing additivedeveloped 2.75 grams of ammoniasoluble lead per 100 ml. oftetraethyllead after storage for one month at 104 F.

The Z-aminodiphenylamine stabilizer of my invention can be incorporatedinto the fuel along with the antiknock compound as described above.However, if it is desired to add the stabilizer to the finished highoctane lead-containing gasoline, I have found that a number of methodsof introducing the stabilizer are effective. For example, theZ-aminodiphenylamine can be directly added to the fuel as it isrecovered during the refinery operation and prior to the addition of thetetraethyllead antiknock compound, or it can be added to the finishedfuel after blending with the antiknock compound. One of my preferredmethods of introducing the Z-aminodiphenylamine which does not affectthe ultimate efliciency of stabilization of the tetraethyllead is in theform of a liquid formulation wherein the amine is predissolved in aketone such as acetone, methylethyl ketone, methyl isopropyl ketone,diisopropyl ketone, diisobutyl ketone and the like wherein theZ-aminodiphenylamine is present in an amount between about 10 and 50weight per cent of such finished liquid formulation. Althoughv it is notessential that the amine be so formulated prior to admixture to the fuelor the antiknock compound, I have found that by so doing the blendingoperation is simplified and uniformity of blending is assured.

The amount of Z-arninodiphenylamine which I employ to protect thetetraethyllead antiltnock additive is not critical from the standpointthat the employment of more than the minimum amount required does notaffect the stability of the resulting mixture. However, a practicalupper limit is imposed on the concentration of the Z-aminodiphenylamineby the requirements mentioned previously of the modern high compressionengine. This is one particular advantage of Z-aminodiphenylamine, inthat it can be employed where other stabilizing compounds Would berequired in too high concentrations to permit use in such engines. Theminimum amount of Z-aminodiphenylamine depends to a large extent uponthe concentration of tetraethyllead in the gasoline and upon thegasoline type. For example in a highly stable gasoline such as theaverage aviation fuel and in the presence of about 4.0 ml. oftetraethyllead per gallon of fuel, 1 prefer to employ myZ-aminodiphenylamine in an amount of between about .02 and 0.2 mg. perml. of fuel. Furthermore, if the gasoline is of the unstable type theamount of Z-aminodiphenylamine will depend somewhat upon thisinstability. If the unstable gasoline has not previously been stabilizedwith a gasoline antioxidant, a larger amount of the Z-aminodiphenylaminewill be required. However, in such cases the amount of2-aminodiphenylamine will be far less than the total quantity of agasoline antioxidant plus 2-aminodiphenylamine which would be required.Thus when Z-aminodiphenylamine alone is used in an unstable gasolinecontaining tetraethyllead a far smaller amount of total stabilizingingredients can be employed than has heretofore been possible withresulting improvement in the operation of the internal combustion engineusing such fuel.

The effectiveness of Z-aminodiphenylamine as a tetraethyllead stabilizeris largely independent of the fuel type. Thus I have obtained equallygood results when employing Z-aminodiphenylamine to stabilizetetraethyllead in such diverse fuels as straight run parafiins,thermally and catalytically cracked high octane gasoline, highlyaromatic aviation fuels and alkylate fractions suitable for use as suchor further blending. In general, when the fuel is more unstable than thetetraethyllead, my stabilizer can eflectively stabilize both thegasoline and the tetraethyllead when present at high enoughconcentrations, or a gasoline antioxidant can be employed to protect thehydrocarbon fuel and the 2-aminodiphenylamine can be employed to protectthe tetraethyllead antilcnock ingredient.

Incorporated directly in the antiltnoclt fluid I can employ as little as0.01 weight per cent of Z-aminodiphenylamine based on the tetraethylleadcontent of such fluid or as much as 3.0 weight per cent. My preferredlimits,

however, are between about 0.05 and 1.0 weight per cent.

Several methods of manufacturing Z-aminodiphenylamine are satisfactory.One method which I prefer comprises the reduction of2-nitrodiphenylamine with iron filings and hydrochloric acid. Othermethods of reduc- 5 tion are similarly effective, for example catalytichydrogenation. The 2-nitrodiphenylamine is readily prepared by nitrationof diphenylamine.

Having thus described typical methods of employing the2-aminodiphenylamine of my invention as a stabilizer 10 fortetraethyllead, for tetraethyllead-containing antiknock compounds andfor tetraethyllead-containing high octane hydrocarbon fuels, I do notintend that my invention be limited except by the appended claims.

I claim:

1. An antiknock composition wherein the principal antiknock ingredientis tetraethyllead and, as a stabilizer therefor, Z-aminodiphenylamine inamount between about .05 and 1.0 part by weight per 100 parts of saidtetraethyllead antiknock ingredient.

2. A hydrocarbon fuel composition containing tetraethyllead as aprincipal antiknock ingredient in amount 5. The composition of claim 2having incorporated therein an aliphatic ketone in amount between about20 and 100 weight per cent of said Z-aminodiphenylamme.

6. The method of preventing instability of a hydrocarbon fuel containingas a principal antiknock ingredient tetraethyllead which comprisesincorporating therein a stabilizing amount of a composition consistingessentially of 2-aminodiphenylamine in admixture with an aliphaticketone, said Z-aminodiphenylamine present in amount between about 10 andabout 50 weight per cent of such stabilizing composition.

7. In combination tetraethyllead and a stabilizing amount of acomposition consisting essentially of Z-aminodiphenylamine in admixturewith an aliphatic ketone, said Z-aminodiphenylamine present in amountbetween about 10 and about 50 weight per cent of such stabilizingcomposition.

8. A liquid stabilizing composition comprising in admixtureZ-aminodiphenylamine and an aliphatic ketone, said 2-aminodiphenylaminepresent in amount between about 10 and about 50 weight per cent of suchstabilizing composition.

9. The composition of claim 8 wherein said ketone is acetone.

References Cited in the file of this patent UNITED STATES PATENTS

7. INCOMBINATION TETRAETHYLLEAD AND A STABILIZING AMOUNT OF ACOMPOSITION CONSISTING ESSENTIALLY OF 2-AMINODIPHENYLAMINE IN ADMIXTUREWITH AN ALIPHATIC KETONE, SAID 2-AMINODIPHENYLAMINE PRESENT IN AMOUNTBETWEEN ABOUT 10 AND ABOUT 50 WEIGHT PER CENT OF SUCH STABILIZINGCOMPOSITION.